Buhler´s Sortex Colour Sorter In Plastics Recycling

01.05.2007 Efficient and cost effective sorting is at the heart of the plastics recycling industry. Across Europe interest in recycling and the awareness of the need to recycle plastic products, particularly bottles, is becoming firmly stamped on the public mind. When you consider that eleven percent of household waste is made up of plastic and that 40% of that is made up of discarded plastic bottles, or that by 2010 one million tons of PET waste will be collected in Europe every year, it is no wonder that the emphasis is firmly swinging away from dumping our old plastic into landfill sites with all the resulting problems of over-fill, and is now heavily in favour of recycling.

In Europe we are making giant strides towards turning most of our waste plastic back into something useful and usable. Materials such as PET, HDPE and PVC are, after all, valuable products and the demand for them is rising rapidly; fortunately PET, HDPE and PVC are, of course, eminently recyclable.

Take AMCOR for instance which has 70 plants globally and makes over 32 billion containers every year - it has a dedicated European facility to recycle PET and to improve and develop the quality of its recycled products. Also at the forefront of the drive to recycle, is Sorepla - which now turns 25% of France's waste PET products every year into re-usable flakes, which will become all kinds of new products as diverse as scouring pads and carpets.

But recycling comes at a price. Foremost among the difficulties and costs of the process is sorting the plastic that can be re-used from that which has no further value, and the trend towards highly coloured plastic used by some drinks manufacturers hasn't helped in this as there is little demand in the recycle market for colour 'contaminated' material.

Even the humble UPVC window frame comes with an attached problem when it comes to recycling the millions that we throw away every year. In this case it is the rubber extrusion, which used to be fitted by crimping and was easily removed by hand before crushing. Nowadays it is co-extruded with the profile and many specialist re-cycling companies have had to resort to time consuming and expensive band saw operations to remove it.

Recycling plastic sourced from items such as PET bottles follows a simple process; it is collected, baled-up for delivery to the recycling plant and there it is washed, rolled and cut into small flakes to be re-sold back into the manufacturing sector. At the heart of this technology is the need for sorting. Impurities must be removed from the product stream including PVC from a PET stream, not to mention paper, glass, aluminium, wood, bottle tops and many other contaminants.

Most larger items can be identified and removed pre-crushing but vital sorting remains to be done after the rolling and crushing process has produced the flakes which will be sent to the end user, and an additional requirement at this stage is to sort the flakes into grades of usable colours.

It's at this point that the plastic recycling industry turns to a technology initially developed for the agricultural industry as long ago as 1947 in London's East End. Today, the original mechanical sorters have evolved into sophisticated colour sorting technology, the leading exponent of which is those original London innovators Sortex, now part of the Buhler group.

Sortex colour sorting machines can identify and reject from a fast flowing product stream, even the most minute differences in shades of colour and they can easily eliminate contaminants and produce separate final product streams of different colours.

Sortex machines such as the Z4V colour sorter used by Sorepla (one of Europe's largest recycling companies), use state of the art optics to achieve a sorting rate of up to 3.5 tons per hour of PET flakes, producing three streams of different coloured pellets - clear; transparent and blue; blue and green mixed. Moreover, Sortex machines can produce an eject stream that contains a very low percentage of good product; this represents a considerable sum of money saved when processing such massive quantities.

And it's not just European giants who benefit; in the UK Peter Penfold, owner of Penfold Plastics, saw a massive cost saving and dramatic increase in his profits when he stopped cutting the rubber seals from UPVC windows and crushed the entire frame and rubber together. He installed a Sortex sorter to then eliminate the rubber pellets from the UPVC ones. His brain-wave saved hours of labour and made a huge impact on his bottom line. Needless to say, others in the UPVC market have turned to Sortex technology to deal with similar contaminant problems.

Today, the name Sortex has become a by-word for efficiency, accuracy and quicker, leaner production. In fact the term "Sortex Standard" is a recognised industry buzzword. It's a long way from 1947 and remarkable to think that Sortex today is still offering elegant solutions to an industry that 60 years ago didn't even exist.